The structure and light-emitting theory of light-emitting diode (LED) are different from that of traditional light source. Comparing to conservative light source, light-emitting diode (LED) has some advantages, e.g. low power consumption, long lifetime, no warm-up time, fast responding. And, light-emitting diode (LED) has small volume and is shake-resistant, suitable for mass production and easy to be adopted in a very small unit or an array unit for application needs. Thus, light-emitting diode (LED) is adapted in various applications, e.g. optical display unit, laser diode, traffic light, data saving device, communication device, and medical device, etc.
The common array light-emitting diode shown FIG. 1 comprises a substrate 8 and a plurality of light-emitting stacks 2 comprising a second semiconductor layer 26, a light-emitting layer 24, and a first semiconductor layer 22 on the substrate 8. When the substrate 8 is insulating, the manufacturing method of the array light-emitting diode comprises the steps of forming the trench 18 between the light-emitting stacks 2 in use of etching process to make each of the light-emitting stacks 2 insulated to each other, etching a portion of each of the light-emitting stacks 2 to reveal the second semiconductor layer 26; for each light-emitting stacks 2, forming a first pad 43 on the exposed area of the second semiconductor layer 26 and a second pad 63 on the first semiconductor layer 22, and forming metal wire 19 for selectively connecting the first pad 43 and the second pad 63 of each of the light-emitting stacks 2 to connect the plurality of light-emitting stacks 2 in series or parallel.
The above light-emitting diode is able to combine with a submount to form a lighting device. The lighting device comprises a submount with at least one circuit; a solder on the submount, by which the above light-emitting diode can be fixed on the submount, and the substrate of the above light-emitting diode electrically connect to the circuit on the submount; and an electrical connecting structure for electrically connecting the pads of the light-emitting diode and the circuit on the submount; wherein the above submount could be lead frame or large mounting substrate for conveniently designing the electrical circuit of the lighting device and increasing the heat dissipation efficiency.
Currently the common light-emitting diode has internal quantum efficiency (IQE) between 50% and 80%, which means about 20% to 50% of the input power cannot be converted to light. When the light-emitting diode is packaged to form a package, a portion of light emitted from the light-emitting diode is reflected or diffused in the package and finally absorbed by the pad of the light-emitting diode. Besides, because the pad on the light-emitting diode obstructs the path of light, a portion of light cannot go outside and the brightness is therefore reduced.